Power electronic devices such as insulated gate bipolar transistors (IGBTs) and silicon-controlled rectifiers (SCRs) are typically cooled by mounting the devices within a housing which is secured to a heatsink or "cold plate". Cold plates are typically formed from a material which is highly thermally conductive, such as aluminum or copper, enabling the cold plate to readily conduct heat generated by the devices away from the devices and to the environment. Generally, heat is conducted by the cold plate to a structure which is designed to transfer the heat to the surrounding air or a liquid via conduction and convection.
A disadvantage with prior art cold plates is that heat transfer from a power electronic device is diminished to some degree because the heat must travel through the base plate of the housing in which the device is enclosed, and across the interface between the base plate and the cold plate before it reaches the cold plate. Heat transfer across the base plate-cold plate interface is highly dependent on the intimacy of the mating surfaces, which in turn is dependent on the flatness of the mating surfaces and the contact pressure generated by the fastener which secures the device to the cold plate. As a result, localized hot spots can occur in the base plate and cold plate, and the power electronic device is subject to higher operating temperatures. To mitigate this effect, larger and thicker base plates are often utilized to better distribute the heat across the base plate-cold plate interface. Thicker cold plates may also be necessary to provide a greater heatsink mass, particularly where more than one power electronic device is mounted to a single cold plate. Unfortunately, the additional weight resulting from increased base plate and cold plate thicknesses is often undesirable, particularly for applications within the automotive and aerospace industries.
Transfer of heat to a fluid flowing through the cold plate is also known. Again, a thermally conductive metal cold blare is typically used, but with one or more passages being formed within the cold plate. As before, heat is conducted from the devices and to the environment via a cooling fluid flowing through the passages. Though enhanced heat transfer is possible with fluid-cooled could plates, such cold plates share the same disadvantage noted above with the more conventional prior art cold plates. Specifically, heat transfer from the power electronic device is diminished because heat must travel through the base plate of the device and across the interface between the base plate and the cold plate before it reaches the cold plate. Consequently, power electronic devices cooled by fluid-cooled cold plates are also subject to higher operating temperatures.
Thus, it would be desirable to provide a method for promoting the heat transfer between power electronic devices and the environment, such that cooler operating temperatures can be achieved for the devices. It would be particularly advantageous to exploit the enhanced cooling capability made possible by fluid cooling a cold plate, yet enhance the overall heat transfer characteristics wit]hour incurring additional weight. Furthermore, it would be advantageous if heat transfer could be selectively enhanced for one or more electronic devices which are enclosed in a housing mounted to the cold plate, so as to enable better control of the operating temperatures of the devices.